1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member which comprises a photosensitive layer containing a resin having a specified structure. The present invention also relates to an electrophotgraphic apparatus, a device unit, and a facsimile machine, employing the electrophotographic photosensitive member.
2. Related Background Art
In recent years, most electrophotographic photosensitive members utilizing an organic photoconductive substance are comprising a charge-generating substance of relatively low molecular weight, such as azo pigments or phthalocyanine pigments, dispersed in a suitable binder resin. Among these organic electrophotographic photosensitive members, a layered type which has functionally separated layers of a charge-generating layer containing a charge-generating substance and a charge-transporting layer containing a charge-transporting substance are widely used because of the sensitivity, potential characteristics, and durability thereof.
In the electrophotographic photosensitive members, the characteristics of the photosensitive member are mainly determined by the efficiencies of carrier-generation and carrier-transportation of the photosensitive member. In the case of the layered type, the characteristics are also determined by the efficiency of carrier-injection. These factors are considered to depend not only on the properties of the charge-generating substance and the charge-transporting substance but also on the the properties of the binder resin. Heretofore, the binder resins have been investigated mostly from the standpoints of the binding properties, the pigment dispersibility, mechanical strength, the solvent-resistance, and so on. Japanese Laid-Open Patent Application No. 62-30254 describes that the electrophotographic characteristics of a photosensitive member, such as sensitivity, potential stability, and residual potential, are affected by the structure, the functional group, the molecular weight, etc. of the binder resin, recognizing the binder resin as a functional resin.
According to the recent requirement for higher image quality and higher durability in photoelectrography, photosensitive members having more excellent properties have been pursued.